1. Field of the Invention
The present invention relates to a filling material to be used for filling a metal or alloy conductor into a minute space and a filling method using the same.
2. Description of the Related Art
As means for realizing a three-dimensional circuit configuration in electronic devices including various scales of integrated circuits and various types of semiconductor devices and chips thereof, there has been proposed a TSV (through-silicon-via) technology of providing a circuit board with a large number of through electrodes and stacking these circuit boards. With the TSV technology, many functions can be packed into a small footprint. In addition, important electrical pathways between devices can be dramatically shortened to facilitate increasing processing speed. Japanese Unexamined Patent Application Publication Nos. 2002-237468 & 2002-368082 disclose a molten metal filling method as a through electrode forming technology essential to the TSV technology.
When using the above molten metal filling method for forming a through electrode in a semiconductor chip or a wafer previously formed with a semiconductor circuit element (via-last), it is necessary to avoid thermal deterioration of the semiconductor circuit element and an accessory organic substance of the wafer due to the heat of fusion. In order to avoid the thermal deterioration, a metal material having a melting point of about 200° C. or less has to be employed as a metal material for forming the through electrode.
In order to realize a three-dimensional circuit configuration, on the other hand, a plurality of wafers obtained by using the TSV technology have to be stacked and joined together in an atmosphere having a temperature of 300° C. or more.
However, while the melting point of the metal material for forming the through electrode is 200° C. or less, the heat treatment temperature for joining the wafers in a stacked state is 300° C. or more, so that the through electrode may be melted at the joining process of the wafers.